The Selkirk Mountains/Chapter 7
CHAPTER VII.
GLACIERS OF THE SELKIRKS.
(From a Monograph by A. O. Wheeler.)
Structure: In popular terms, a glacier is a river of ice draining a rock-basin above tilled to overflowing with ice and snow and technically known as névé or firn but popularly called a snow-field. The area of the Illecillewaet Snowtield is about 10 square miles, but there are many smaller in the Rocky Mountain system and some much larger, notably in the north, to wit, the Columbia Snowfield roughly estimated to cover 200 square miles at a mean altitude of 10,000 feet.
In these high regions, the heavy precipitation is always in the form of snow which keeps the great rock-basins full to over-flowing. The prodigious weight of the mass compacts the under-snows into clear crystal ice. To illustrate: if you take a handful of snow, squeeze it until it becomes a transparent crystal and then let it freeze, you have the counterpart of glacier-ice.
This overflow pushed slowly down the mountain by the enormous pressure from above constitutes the glacier—is the glacier. Its upper part is covered with snow, and its lower part, where the warmer air melts the surface-snow, is exposed ice. This is the "ice-fall" and. in contrast to the snow-covered part, is called "dry-glacier". Heat and cold, contraction and expansion, and the unevenness of the bed over which it moves downward, cause large cracks to occur across the ice-river. They are of all sizes and are called crevasses. Sometimes they cross each other, and the result is that when the pressure from above closes the cracks, great ice-pillars of fantastic shapes, called seracs. are formed. The flow of a glacier is just like that of a river: the centre of the stream moves faster than the sides or bottom: while on a curve the outside edge flows more rapidly than the inside. Again, at a narrow place, the flow is faster and the glacier is broken and cracked, resembling the broken water of a rapid.
Moraines are the piles of mud, rock, and loose boulders always along the sides, at the end (tongue, snout or forefoot), and sometimes in the middle of a glacier; and called respectively lateral, terminal and medial moraines. The materials of which they are formed have fallen from surrounding cliffs and, through the course of ages, have been carried by the glacier and deposited in their places in somewhat the same manner as a rapid stream or river deposits along its shores driftwood and detritus; only the flow of the glacier is very, very slow, a few feet in the year, and the process of piling up has taken ages. If the rate of the flow of the glacier over its rocky bed, caused by gravitation and pressure from above, is greater than the annual loss by melting during the summer, the glacier is advancing; if less, it is retreating.
In 1898 a supplementary minute-book was opened at Glacier House for the purpose of recording matters of general scientific interest. Among the first entries made is a general statement by the late Wm. S. Vaux, Jr., of the series of investigations carried on by himself, his brother and Miss Vaux in connection with the
movement, rate of flow, and general change of appearance of the Illecillewaet and Asulkan Glaciers.
It is aimed in this statement, illustrated by photographs and a map, to supply information that will enable interested visitors to make intelligent observations carrying them on from where they were last left off, and so to enter their records in the book.
The lllecillewaet Glacier.
The investigations carried on by Messrs and Miss Vaux deal chieily with the two principal movements of glaciers—the rate of How and the advance or retreat of the forefoot. The third study dealing with changes in the general appearance of glaciers is best conducted by means of photographs taken year by year from the same position.
The Messrs and Miss Vaux began observations on the lllecillewaet Glacier on July 16, 1887, and took a number of photographs, now of special interest and value. At that time the forefoot came down to within 20 feet of the alder bushes; and a great mass of ice with steeply sloping sides covered what is now a long stretch of bare moraine. The general conditions then pointed to a recent period of advance.
In 1888, Mr. W. S. Green and the Rev. H. Swanzy included in their topographical survey some observations on this glacier. Holes were bored in the ice and a row of poles set up. Twelve days afterwards, all the poles had fallen, owing to the surface melting at their bases. The bottom of the holes was found in a few cases, the poles set up and observations taken. It was then ascertained that a pole near the moraine had in twelve days moved seven feet, one further out ten feet, and one in the centre twenty feet. From two rows of boulders dropped in front of the snout, it was deduced that the glacier had retreated about sixty feet during that past year, and from the inner row within that present year (1888). Mr. Green concluded his observations by tarring some of the boulders in closest proximity to the ice, so that the future retreat might be observed by other travellers. (W. S. Green's "Among the Selkirk Glaciers.")
In 1890 Mr. Harold W. Topham also made some observations on the same glacier, and at the close of his article in the Alpine "Journal" (May, 1891) makes the following request:—"In conclusion. I will ask any one intending to visit the Selkirks to obtain from me certain data, which will enable him to continue the observations which I commenced for the measurement of several of the glaciers."
In 1894, the Messrs. Vaux renewed their observations and with few omissions have continued them regularly until the present (1911).
In 1899, Mr. W. S. Vaux made an instrumental survey of the Illecillewaet Forefoot and its vicinity, and published a map. The copy here reproduced, which is corrected to July, 1906. will be useful in all future observations. At the time of this survey eight metal plates were placed in line across the glacier at right angles to its flow, where it was about one-third of a mile wide.
A base of 229 feet 6 inches was then measured on the high 
The Illicillewaet Glacier (Black line on raock shows where the ice rested in 1887)
Tongue of the Illicillewaet Glacier (1898)
right-hand moraine about 1,000 feet above the snout of the glacier, a transit-theodolite set up at each end, and readings taken to each plate. A base also of 334 feet 6 inches was measured on the ground moraine in front of the forefoot and a number of points fixed by readings from both ends. In addition, the relative positions of a number of marked rocks, and rocks for future reference were located. (See map.)
As a result of observations made at intervals from 1899 to 1906, it has been computed that the average greatest daily movement of the ice down its bed, is 5.9 inches, or 179.4 feet per year.
On the map, directly in front of the most advanced portion of the ice-forefoot, will be noticed a rock marked "C". From this rock yearly measurements have been made to the nearest ice. The table below shows the annual recession from 1898 to 1910.
Illecillewaet Glacier—Recession of Tongue of Ice from Rock "C".
| Date of Observation. | Distance Tongue of Ice to Rock "C" | Recession of Ice since previous year. | |||||
| August 17, 1898 | 60 | ft. | |||||
| July, 29, 1899 | 76 | ft. | 16 | ft. | |||
| August 6, 1900 | 140 | ft. | 64 | ft. | |||
| August 5, 1901 | 155 | ft. | 15 | ft. | |||
| August 26, 1902 | 203 | ft. | 48 | ft. | |||
| August 25, 1903 | 235 | ft. | 32 | ft. | |||
| August 14, 1904 | 240 | ½ | ft. | 5 | ½ | ft. | |
| July 25. 1905 | 243 | ft. | 2 | ½ | ft. | ||
| July 24, 1906 | 327 | ft. | 84 | ft. | |||
| August 12, 1907 | 316 | ft. | 11 | ft. | Advance | ||
| September 26, 1908 | 355 | ft. | 39 | ft. | Recession | ||
| August 21, 1909 | 366 | ft. | 11 | ft. | Recession„ | ||
| August. 1910 | 426 | ft. | 60 | ft. | Recession„ | ||
The Asulkan Glacier.
Observations taken on the Asulkan Glacier by the Messrs. Vaux were on the same lines as those on the Illecillewaet, but they have not been continuous and no attempt was made to measure the rate of flow until 1906. In 1901 there was a distinct advance which continued for about three years when recession began again. This advance interfered with the observations, the large boulders in the moraine marking the datum-line being shoved forward by the advancing ice and entirely obliterating the base-line used for measurements.
The average greatest daily motion of the ice has been computed at 6.7 inches, or very nearly 204 feet per year. It was found on the 21st August, 1909, that the advance had been so great as to obliterate the marked rocks that had been used since 1899.
The Illecillewaet and Asulkan Glaciers are the only two on which measurements and observations have yet been taken, owing, no doubt, to their accessibility from Glacier House. Many glaciers of approximate magnitude difficult of access, offer most interesting studies, among them the Bonney, Rogers, Geikie, Deville, Grand, Beaver and Duncan Glaciers.
The Selkirk Glaciers are comparatively small but very numerous. They are remarkable for their purity and are not, as a rule, defaced by moraines or covered by rock debris. Particularly remarkable are the vast number of hanging glaciers. Along the heads of the high valleys they are found lining the sides, and are strikingly beautiful in the labyrinthine structure of their crevassed surfaces, which from a distance resemble a creamy film of lace-work enshrouding bare rock. Compared with the great glaciers of Alaska, of the Himalaya, and of other great mountain systems, they are puny; but even so, they have distinctive features all their own that give them a prominent place in the study of those parts of the earth that are covered by ice.
A NOTE ON THE GEOLOGY OF THE SELKIRK MOUNTAINS.
The Geological Survey of Canada has done very little work in the Selkirk Mountains, and the only report on them was made by Dr. Dawson about twenty years ago. Following the C.P.R. from west to east there are first about seventeen miles of very ancient rocks, granites and gneisses of the Archaean. These rocks, with the nearer parts of the Gold Range to the west, represent the old nucleus or "protaxis" of the western ranges. They probably formed an important mountain range in the earliest times, but being so old, have suffered the penalty of age in mountains and have been greatly cut down.
Following the granites, eastwards there are 15,000 feet of dark slate and schist, once muddy sediments on a sea bottom, now thrown into folds, first a syncline or downward fold, afterwards an anticline or upward fold. Then come lighter colored series of quartzites and conglomerates, often schistose with the shimmer of mica scales. Near the summit these rocks make a syncline, but toward Beaver Creek they have been bent into an anticline and broken across by a great fault. The thickness of these rocks Dr. Dawson puts at 25,000 feet.
Coming out towards Donald there are later rocks (Cambro-Silurian) also folded and transformed largely into lustrous slates. Fossils are so rarely found in the Selkirks that the age of these thick deposits is quite uncertain. Dr. Dawson calls everything Cambrian between the granite and the eastern Cambro-Silurian. The granite and gneiss of the western Selkirks are very ancient eruptive rocks, highly crystalline and formed far below the surface. It is rather remarkable that there are very few undoubted eruptive rocks farther east and none along the line of the railway. In the Gold Range to the west there were great volcanic eruptions with lava shoots and thick beds of ashes after the Selkirks had been elevated, and there are important volcanic areas in the southern Selkirks, toward the Boundary.
As the Selkirks are a very old range, far older than the Rockies, they have undergone much destruction, and the great glaciers of the Ice Age had much to do with the moulding of the slopes and valleys, and the carving of the beautiful lake basins. (Dr. A. P. Coleman, in the Canadian Alpine Journal.)
THE SNOW-SHEDS OF THE SELKIRKS.
Owing to the heavy precipitation and consequent enormous accumulation of snow during the long winter, on the mountains of the Selkirks, the avalanche is a distinct danger to the railway in the narrower valleys and passes. In the spring the snow may weigh almost 50 lbs. per cubic foot, and very little will start an avalanche. Its powers of destruction are terrible. Therefore, wherever there is exposure, the track is protected by snow-sheds. Albeit built for stern utility without regard to beauty, their achitecture is of interest. Indeed, looking through the long vista of an interior, the lines of its rafters are not unbeautiful.
There are five types of snowsheds. (1) If the surface is at a steep angle the uphill side is held by a retaining crib of cedar logs. The rafters are supported by one end of this crib, and the other end is carried by a framed bent, the middle of the rafter being supported by struts. As a rule, the bents are five feet apart between centres, but at places where unusually severe avalanches may be expected, the distance is reduced to four. Shed rafters are usually of Douglas fir and are 12 by 15 inches in size, the plumb and batter posts being 12 by 12. The bents are supported either by piles or mud sills.
The second type is made to suit a flatter slope. The crib is only carried up half way, and a framework of posts and rafters is built on top. In the third type the crib is omitted altogether. In the fourth, known as the "valley-type" and built to resist avalanches from either side, the cribs are built on both sides and the rafters laid directly across. The fifth type is used for those places where the track is cut out of the hill-side and where the avalanche must fall nearly vertically on the snowshed. Its rafters are trussed and the sheds more strongly built.
As snowsheds are subject to fire, ample fire protection is provided. There is a complete system of piping throughout, and the shed itself is broken into short lengths separated by fire-breaks. These breaks are covered by split fences made of heavy V-shaped cribs to guide the slide over the adjacent sheds. There is also a thorough system of patrol and should fire break out a watchman would be on the spot speedily.
There are altogether six miles of snowsheds from six miles east of Rogers Pass to fifteen miles west of Revelstoke in the Gold Range. The average cost of building is some $40 a foot.